1. Field of the Invention
At least one embodiment of the invention relates to a catheter arrangement having a catheter, in particular ablation catheter, with an optical force sensor, which is integrated in the distal section thereof and which is configured and arranged to measure an external force acting on the distal section.
2. Description of the Related Art
In certain fields of use of catheters or similar devices, e.g. electrode lines, a pressing force applied to adjacent tissue is important for the functionality of such devices, therefore detection of this contact force is of interest. This applies in particular to ablation catheters by means of which tissue areas are atrophied or tissue parts are ablated.
An example of an ablation catheter is Enclosense's “TactiCath®” that enables measuring a force acting on a distal catheter end during an ablation process in terms of amount and direction. A catheter of this type utilizes the principle of the so-called FBG (Fiber-Bragg-Grating) sensor, wherein three fibers, each with one FBG sensor at the fiber end, form a group of sensors, which is necessary for a 3D force measurement. For joint measuring signal processing, the sensors can be connected to a signal processing unit. The sensors are attached at an angular distance of 120° on the outside of a deformable cylinder.
In Patent Application Publication No. U.S. 2008/0285909 A1, the functionality of FBG sensors for determining twistings or curvatures of the catheter body, is described in detail and also the functionality of the aforementioned force sensor with a plurality of FBG fibers attached to a deformable cylinder is explained.
In International Patent Application Publication WO 2009/138957 A2, temperature compensation by means of electrical thermocouples is provided because with the FBG measurement method, even small temperature changes or deviation between the individual sensors can cause significant measurement uncertainties. Also, during an electrothermal ablation process, considerable temperature fluctuations can occur at the tip of the ablation catheter. It is also known from the mentioned printed matter to reduce the thermal conductivity between the ablation head of an ablation catheter (which can become very hot) and the force sensors in order to reduce the effect of temperature changes on the result of the force measurement. In each case, the structure of the catheter is extremely complex resulting in high production cost for the catheter itself and also for the associated evaluation unit.
The optical measurement principle of FBG sensor systems is generally known and also known in particular in connection with its use for force measurements and temperature measurements; cf., for example, www.wikipedia.org/wiki/Fiber_Bragg_grating and U.S. Pat. No. 5,399,854.
Applicant's co-pending U.S. Patent Application Publication. 20120220879 A1, discloses a catheter, a catheter arrangement and a force measuring device, wherein an individual FBG fiber fixed in a sensor holder comprises three force sensor regions that form force sensors for joint measuring signal processing, and wherein, in addition, a T sensor region can be provided on the fiber.